Product Feature 1
Jack Browne, Technical Director
decreasing temperature, reaching extremely low
values at cryogenic temperatures. This behavior
CRYOGENIC COOLING can often improve the has long benefited satellite-communications (sat-
performance of electronic components and sys- com) operators where the sensitivity of the receiv-
tems. Unfortunately, achieving the extremely low er depends on the noise figure (or noise tempera-
temperatures needed to essentially ture as it is commonly known in sat-
affect electron behavior is often cost- com systems) of the low-noise ampli-
ly and generally requires large refrig- fier (LNA). In military applications,
eration units that consume generous HTS sensors and infrared imaging
amounts of power. Because of the systems rely on cryogenic tempera-
need for small and cost-effective tures for optimum performance.
cooling units in both commercial and Traditionally, liquid nitrogen has
military systems, Superconductor 1. The Sapphire cry- been used to achieve cryogenic tem-
Technologies, Inc. ocooler is a compact, peratures in laboratory settings,
low-power unit that is
( www.suptech.com) has developed a ideal for use with IR although containing and managing compact cryocooler called Sapphire sensors and HTS-based liquid nitrogen in the field is not trivial. that delivers the low temperatures components and sub- Alternatively, bulky Joule Thomson needed to achieve superconducting systems. and Gifford McMahon cryostats have behavior in electronic circuits but is efficient in also been used, albeit with limited reliability. terms of power consumption. The Sapphire cryocooler is based on Free-
The Sapphire cryocooler (Fig. 1) was nominally Piston Stirling cryocooler technology, now consid-developed for use with the firm’s line of high-tem- ered fairly mature due to numerous advances and perature-superconductor (HTS) materials, compo- developments during the 1990s. With over 5500 nents, and subsystems, but can serve any system units in the field running full time in cellular base or module that benefits from operation at cryo- stations, the reliability of the Sapphire cryocooler genic temperatures. In amplifiers, for example, the has been proven under real-life conditions and in noise figure of gallium arsenide increases with real operating systems. In fact, the Sapphire cry-elevated temperature and decreases with ocooler has a mean time before failure (MTBF) of
Input power—W
120 100 80 60 40 20
0
0
Treject
°C
Treject = 42°C
123456
Heat lift—W
better than 1 million hours based on this actual field data, and requires no maintenance.
The Sapphire cryocooler measures just 3. 6 11. 8 in. (92 300 mm) and weighs only 6. 2 lbs. ( 2. 8 kg) but provides the performance of much larger units with a cooling capacity of 5 W heat lift at 77 K (Fig. 2), essentially maintaining that 77 K temperature at low input power levels.
The unit is designed to handle vibration levels equivalent to 10 N of transmitted force, but can be modified for lower levels. It runs at ambient temperatures from –40 to +60ºC. Superconductor Technologies, Inc., 460 Ward Dr., Santa Barbara, CA 93111; Internet: www.suptech.com.
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